At a first glance Michael and Sonny appear to be quite different. Upon further observation, however, they have some similarities. Although they are different in areas of personality, values, and their tempers, they are similar in areas of loyalty, their respect for their father, and their strong family ties.
Their personalities are quite different. Sonny is brash and arrogant, where Michael is calm and cool. When Don Corleone was in the hospital and Sonny is in charge, the family got kind of careless. He doesnt seem to care what could happen due to his actions. He wants to kill the police captain and doesnt think about the repercussions. Tom has to tell him that it wouldnt be good to kill a cop, but they end up doing it anyway. I think Michael was pushed into it because of his loyalty to the family. He is more calculating in manner. Near the end when he takes care of all the family business on the day of the Baptism is a prime example of this. Because he was this way, the objects of his violence had no idea that it was coming.
Their values are another way that they differ. Michael is a man of honor. He doesnt run around having affairs with different women. He only marries twice because his first wife was killed in the explosion. Sonny is an adulterer. He is with another women during his sisters wedding, along with a few other times throughout the movie.
Their tempers were not nearly the same. Sonny had a bad temper, while Michael did not. Sonnys temper ended up getting him killed. He flew off the handle when he found out that his sister had been beaten and ran out of the house without anyone with him. During those times he should have known better, but all he had on his mind was vengeance. Michael on the other hand is fairly calm about things. He knows that Carlos was involved in Sonnys death, but he lets it go until it is time to deal with it.
They are similar in loyalty. They do what they need to do for their friends and family. When others help them out, they do the same. Although Sonny felt that the move towards narcotics was a good idea, he didnt go in that direction when he was in charge.
They both had great respect for their father. When he wanted something done they jumped. When He was shot, Michael rushed home to see if he could help. He eventually got involved in the family business because of this. Sonny wanted the people who had been involved in the shooting to pay at all costs.
Finally they both had strong family ties (towards the Corleone family). When a member of the family needed something they gave it to them. Sonny was outraged to learn that his sister was the victim of spousal abuse, and wanted to get her husband for it. They did everything they could to make sure that every member of the family was safe at all times. Michael even gave up a whole year of his life to avenge his fathers shooting. He had to go to Italy to hide out afterwards.
In conclusion, Sonny and Michael were two completely different people, with different traits. They had different ways of doing things, but in all of that they remained so much the same. I think that has to do with the way their Father brought them up, because I feel that he was the role model that they were molded after.